In therapy of a heart disease possibly involving coronary artery stenosis, a radiopaque material (contrast medium) is given (injected) to the supposed stenosis portion of the coronary artery so as to check the stenosis state. In dosing with the radiopaque material, the radiopaque material may be diluted with a diluting liquid, for example, physiological saline. As an apparatus for diluting the radiopaque material with a diluting liquid, i.e., mixing the radiopaque material with a diluting liquid, for example, a radiopaque material injecting apparatus described in Patent Document 1 has been known.
The radiopaque material injecting apparatus has a three-way stopcock train which is connected to a catheter set indwelling in the patient and in which a plurality of three-way stopcocks are connected, and a plurality of tubes connected to the three-way stopcock train.
Each time of dosing with the radiopaque material by use of the radiopaque material injecting apparatus, a vessel filled with the radiopaque material and a vessel filled with the diluting liquid are connected to relevant tubes. There may be cases where these connecting operations are not conducted in a space where sterile conditions are maintained (sterile room). In such a case, the radiopaque material and the diluting liquid cannot be mixed in a sterile manner.
In addition, a cock for selecting opening/closing of liquid flow passages, i.e., for changing over the liquid flow direction, is disposed in each of the three-way stopcocks. Besides, each of the tubes is equipped with a roller clamp for opening/closing the tube. In using the radiopaque material injecting apparatus, cock opening/closing operations and roller clamp opening/closing operations are conducted in combination at the time of mixing the radiopaque material and the diluting liquid. Therefore, the radiopaque material injecting apparatus has been complicated to operate, and it has taken a long time to achieve dosing with the radiopaque material diluted with the diluting liquid. In short, it has been impossible to speedily dose with a radiopaque material diluted with a diluting liquid.    Patent Document 1: Japanese Patent No. 3195314